Datasheet

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SBOS383C − DECEMBER 2006 − REVISED MAY 2008
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11
STATUS REGISTER
The TMP411 has a Status Register to report the state of
the temperature comparators. Table 4 shows the Status
Register bits. The Status Register is read-only and is read
by reading from pointer address 02h.
The BUSY bit reads as ‘1’ if the ADC is making a
conversion. It reads as ‘0’ if the ADC is not converting.
The OPEN bit reads as ‘1’ if the remote transistor was
detected as open since the last read of the Status Register.
The OPEN status is only detected when the ADC is
attempting to convert a remote temperature.
The RTHRM bit reads as ‘1’ if the remote temperature has
exceeded the remote THERM limit and remains greater
than the remote THERM limit less the value in the shared
Hysteresis Register; see Figure 18.
The LTHRM bit reads as ‘1’ if the local temperature has
exceeded the local THERM limit and remains greater than
the local THERM limit less the value in the shared
Hysteresis Register; see Figure 18.
The LHIGH and RHIGH bit values depend on the state of
the AL/TH bit in the Configuration Register. If the AL/TH bit
is ‘0’, the LHIGH bit reads as ‘1’ if the local high limit was
exceeded since the last clearing of the Status Register.
The RHIGH bit reads as ‘1’ if the remote high limit was
exceeded since the last clearing of the Status Register. If
the AL/TH bit is ‘1’, the remote high limit and the local high
limit are used to implement a THERM2
function. LHIGH
reads as ‘1’ if the local temperature has exceeded the local
high limit and remains greater than the local high limit less
the value in the Hysteresis Register.
The RHIGH bit reads as ‘1’ if the remote temperature has
exceeded the remote high limit and remains greater than
the remote high limit less the value in the Hysteresis
Register.
The LLOW and RLOW bits are not affected by the AL/TH
bit. The LLOW bit reads as ‘1’ if the local low limit was
exceeded since the last clearing of the Status Register.
The RLOW bit reads as ‘1’ if the remote low limit was
exceeded since the last clearing of the Status Register.
The values of the LLOW, RLOW, and OPEN (as well as
LHIGH and RHIGH when AL/TH is ‘0’) are latched and will
read as ‘1’ until the Status Register is read or a device reset
occurs. These bits are cleared by reading the Status
Register, provided that the condition causing the flag to be
set no longer exists. The values of BUSY, LTHRM, and
RTHRM (as well as LHIGH and RHIGH when
ALERT
/THERM2 is ‘1’) are not latched and are not cleared
by reading the Status Register. They always indicate the
current state, and are updated appropriately at the end of
the corresponding ADC conversion. Clearing the Status
Register bits does not clear the state of the ALERT
pin; an
SMBus alert response address command must be used to
clear the ALERT
pin.
The TMP411 NORs LHIGH, LLOW, RHIGH, RLOW, and
OPEN, so a status change for any of these flags from ‘0’
to ‘1’ automatically causes the ALERT
pin to go low (only
applies when the ALERT
/THERM2 pin is configured for
ALERT mode).
Table 4. Status Register Format
STATUS REGISTER (Read = 02h, Write = NA)
BIT # D7 D6 D5 D4 D3 D2 D1 D0
BIT NAME BUSY LHIGH LLOW RHIGH RLOW OPEN RTHRM LTHRM
POR VALUE 0
(1)
0 0 0 0 0 0 0
(1)
The BUSY bit will change to ‘1’ almost immediately (<< 100µs) following power-up, as the TMP411 begins the first temperature conversion. It will be high whenever
the TMP411 is converting a temperature reading.